Wearable Motion Charging Circuit for Small-Battery Power Density
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Solution Overview
Problem
Wearable computing devices face limitations in battery size and power density due to the need for external charging, which restricts rapid charging capabilities.
Innovation Solution
A charging system within the device generates alternating current power from user motion, converts it to direct current using a rectifier circuit, and stores it in an energy storage device with higher power density than the rechargeable battery, transferring charge via a solid state switch when conditions are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the rechargeable battery size is increased to provide sufficient power, then the power density and energy storage capacity are improved, but the device form factor and wearability are worsened
Solution Approach 1:
The battery system is segmented into two distinct components: a small rechargeable battery for base power needs and a larger energy storage device for excess energy accumulation. This segmentation allows each battery to be optimized for its specific function while keeping the overall device form factor manageable.
Solution Approach 2:
The patent implements a nested battery configuration where the rechargeable battery and energy storage device are disposed within the same housing cavity. The energy storage device is positioned to utilize available space efficiently, with both batteries nested within the constrained form factor of the wearable device.
2Productivity
If external charging cables and pins are used for charging, then the charging infrastructure is simple, but the charging speed and convenience are limited
Solution Approach 1:
The device enables self-charging through an exercise detection device that detects user motion and automatically generates electrical energy through an alternating current generator. The system converts mechanical energy from user exercise into electrical energy, eliminating the need for external charging cables and enabling rapid recharging during physical activity.
Solution Approach 2:
The charging process operates periodically based on user exercise patterns. The exercise detection device continuously monitors motion, and the alternating current generator produces electricity during active periods when the user is exercising, allowing the battery to be recharged in periodic intervals throughout the day.
3Power
If a single battery is used, then the device structure is simple, but the energy management and power density are insufficient
Solution Approach 1:
The system performs preliminary energy storage by capturing and storing excess energy generated during exercise in the energy storage device before it is needed. The solid state switch pre-charges the energy storage device during active periods, so that energy is readily available during inactive periods when the device needs power.
Solution Approach 2:
The solid state switch acts as an intermediary component that selectively couples the rechargeable battery and energy storage device. It controls the flow of electricity between the two batteries and to the load, enabling efficient energy management and maximizing power density through intelligent energy routing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables self-charging without external power sources, reducing the size of the onboard battery and allowing for efficient energy transfer, thus overcoming form factor and power density constraints.
Implementation Method 1
The rotor is rotatable relative to the stator due to motion of a user wearing the wearable computing device
Implementation Method 2
The rectifier circuit is configured to convert the alternating current power to direct current power
Data Source
AI summary
A wearable computing device is provided. The wearable computing device includes a housing and a rechargeable battery disposed within a cavity defined by the housing. The wearable computing device further includes a charging system disposed within the cavity. The charging system includes an alternating current (AC) generator configured to generate alternating current power. The charging system includes a rectifier circuit electrically coupled to a stator of the AC generator. The rectifier circuit is configured to convert AC power to direct current (DC) power. The charging system includes an energy storage device electrically coupled to the rectifier circuit such that the energy storage device is charged with the DC power. The charging system includes a solid state switch configured to selectively couple the energy storage device to the rechargeable battery to transfer charge from the energy storage device to the rechargeable battery.